Dysmetria is lack
of coordination of movement typified by under- or over-shooting the intended
position with the hand, arm, leg or eye. Dysmetria of a hand can make writing
and picking things up difficult or even impossible. Dysmetria that involves
undershooting is called hypometria and overshooting is called hypermetria.

Dysmetria is a closely
related condition to intention tremor,
where the constant overshoot causes shaking when performing fine movements.
Ocular dysmetria, where movements of
the pupil of the eye constantly overshoot,
can make it difficult to fix your gaze on an object. Nystagmus,
shaking eyes, is a related condition to ocular dysmetria.

In Multiple
Sclerosis, dysmetria is usually caused by lesions
in the cerebellum, the region of the brain
responsible for coordinating movement, though it can also be caused by
lesions in sensory nervous pathways leading to the cerebellum or the motor
pathways leading from it.

Dysmetria is a difficult
condition to treat although Isoniazid and Clonazepam
work for some.

Many people with
MS have reported great results from small regular doses of cannabis. Cannabis
spray trials in the UK in 2001 also indicate a potential role for the drug
in the treatment of dysmetria and intention tremor though, at the time
of writing (November, 2001), no specific studies on cannabis and dysmetria
have been done. It should be noted that cannabis is and illegal drug in
many countries even for medical purposes, though this position is slowly
changing.